LDraw.org has a tutorial on converting LDraw parts to LDD parts. There are caveats, of course. LDraw unofficial parts have to be handled differently than the official parts. Sometimes color conversion problems and other bugs pop up as well.
We'd be interested in hearing from folks who have done successful conversions, especially those involving NXT creations.
Yes, I personally noticed that a lot of beams were missing as well.
I hope LEGO continues to refine the conversion capabilities from Ldraw to LDD--it would make LDD a more useful product for NXTers.